This invention relates to couplings for quickly joining or separating fluid conducting lines.
Quick disconnect couplings are frequently used in a variety of fluid transfer systems, including both high pressure and low pressure systems and gas and liquid systems for quickly and relatively conveniently connecting and disconnecting the fluid flow supply and discharge lines. Many of these couplings are equipped with automatic means to shut off the flow of liquid when the mating parts of the quick-disconnect device are disconnected.
Quick-action couplings typically comprise two primary components, or members: a generally cylindrical socket having an axial fluid flow passage that is attached to one line and a generally cylindrical plug also having an axial fluid flow passage that is attached to the other. The plug is inserted into the socket to join the two lines and to create a single fluid flow passage between the lines. Generally speaking, the socket has a plurality of evenly spaced locking balls contained in apertures that form a circle around the plug receiving end of the socket. A spring biased detent sleeve circumscribing the socket holds the locking balls radially inwardly. To insert the plug into the socket, the operator first uses one hand to pull the detent sleeve longitudinally away from the plug receiving end of the socket so that the balls are released. Using the other hand, the operator inserts the plug into the socket. The plug has an annular groove, or race, for receiving the locking balls. The operator then releases the detent sleeve, which holds the balls in the annular groove and the plug, and secures the plug in the socket. The operator removes the plug from the socket in an analogous fashion.
Valves are typically included in the fluid flow passageway to urge the plug out of coaxial coupled relation and stop the fluid flow when the plug and socket are released from coaxial coupled relation. Conventional valves typically are fixedly mounted on a valve stem. The valve stem is mounted in a valve guide, also called a spider, that axially locates the valve stem and valve within the coupling member. A coil spring is generally mounted over the valve stem and urges on one end against the spider and on the other end against the base of the valve to urge the valve into contact with the wall of the coupling member to shut off flow. When the coupling members are joined, the valve is typically urged against the bias of the spring and away from the wall of the coupling member to provide a fluid flow passage around the valve.
However, in some fluid flow situations, it is desirable to more definitely preclude backflow of fluid into the supply line so that contamination of the supply is precluded. For example, high fructose corn syrups are frequently used in food preparation. High fructose corn syrups can be subject to contamination by the growth of various organisms, including bacteria and molds, that can effect the taste of the food product or present an unsanitary condition.
To solve this and other problems where backflow is undesirable, check valves have typically been placed in fluid flow lines. Check valves are generally placed in the line in close proximity to a fluid coupling. Check valves are unidirectional flow control devices that eliminate potential damage caused by fluid back pressure and also can assist in precluding contamination of the supply side of the line. For example, the Quick Coupling Division of the Parker Hannifin Corporation offers check valves for use in hydraulic system applications. These check valves have a unidirectional flow path that is blocked by a poppet valve. Crack pressure is set at some desirable level, such as 5 psig in a low pressure setting, to allow the check valve to perform special circuit functions or to operate under particular pressure settings. In a typical hydraulic circuit, the check valve is used to protect the pump by preventing backflow from returning to the outlet port of the pump.
It is somewhat inconvenient to mount separate quick disconnect couplings and check valves in a fluid flow line. It would be desirable to reduce the number of components that are required and the costs and complications of using multiple components to complete a flow circuit.
The invention relates to a quick disconnect fluid coupling that has an integrated check valve. A pressure-actuated check valve is included in the flow path in the coaxial coupling that precludes flow through the coupling below a specified pressure differential and that also precludes flow when the coupling members are separated from each other.
The check valve can be included in either the plug or socket portions of the coaxial coupling and is normally mounted in the downstream member of the coupling. The check valve is mounted on a valve stem axially secured by a valve guide and slides on the stem in response to the pressure of the fluid being supplied through the upstream member of the coupling. The valve will close to prevent backflow when the pressure differential across the valve drops below a predetermined amount. The valve also is closed when the members of the coupling are separated. A conventional valve can be included in the other coupling member, if desired, to open the fluid passageway in that coupling member when the coupling members are in coaxial coupled relation and to shut off flow if the coupling members are separated. The conventional valve is opened by engaging the stem upon which the check valve is mounted when the coupling members are coupled.
Thus, the invention provides a one-piece check valve/coupling combination. The single unit of the invention withstands the rigors of high flow while maintaining ease of installation. The number of components is reduced. Additional space is made available in an enclosed working environment where space issues are sometimes critical. The unitary check valve and coupling also provides for easy replacement of components and for reduced maintenance expense and effort. The check valve of the invention is useful in both liquid and gas applications and at crack pressure typically of from about 5 to 130 psig.